1. Field of the Invention
The present invention relates to an independently controllable transmission mechanism. More particularly, the present invention relates to the independently controllable transmission mechanism utilizing two planetary gear trains for variably controlling power input and output.
2. Description of the Related Art
Taiwanese Patent Pub. No. 1242521 discloses a conventional gearbox structure for vehicles, including a main shaft on which to provide a slide. A forward gear and a drive gear are arranged at each side of the slide. A transmission shaft is provided with a reverse slide and a combination of a backward bevel gear and a forward bevel gear adjacent to the reverse slide. A final gear shaft is arranged between the backward bevel gear and the forward bevel gear. The forward gear and the drive gear are also arranged between the backward bevel gear and the forward bevel gear such that a width of the gearbox can be significantly reduced. Furthermore, the backward bevel gear and the forward bevel gear are used to engage with a transmission bevel gear provided on the final gear shaft so as to minimize the size of the gearbox. With regard to the problematic aspects naturally occurring during use of the gearbox system, the transmission in the gearbox system is susceptible to inefficiency due to the fact that the slide must result in frictional slide movements in the gearbox.
U.S. Pat. No. 6,387,004, entitled “Continuously Variable Transmission,” discloses a continuously variable transmission system, including a first planetary gear train and a second planetary gear train. The first planetary gear train and the second planetary gear train are used to correspondingly transmit powers, which are generated from a first motor and a second motor, to a transmission shaft. However, the primary problem with such a transmission system is due to the fact that the powers generated from the first motor and the second motor must be constantly transmitted to the single transmission shaft via the first planetary gear train and the second planetary gear train. In this manner, the transmission shaft is fixedly designated as a single power input end while the first motor and the second motor are designated as two power input ends. The transmission system, however, cannot be functioned to variably control the power output. Hence, there is a need of providing an independently controllable transmission mechanism for variably controlling the power input, and for variably controlling the power output.
As is described in greater detail below, the present invention intends to provide an independently controllable transmission mechanism utilizing two planetary gear trains for variably controlling power input and output. The transmission mechanism includes a power output end, a transmission control end, a power input end and a free transmission end. The transmission mechanism is capable of shifting the free transmission end between a power input end and a power output end for independently controlling the power transmission. The transmission mechanism of the present invention can avoid using any additional frictionally sliding member so as to achieve increasing the efficiency of power transmission.